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The Complete Blood Cell Count (CBC) CBC - Part 1 The Hemogram

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The Complete Blood Cell Count (CBC) CBC - Part 1 The Hemogram
The Complete Blood Cell Count (CBC)
CBC - Part 1: The Hemogram
A Clinical Pathology 201 Study Module
by
Carolyn Sue Walters, MHS, MT(ASCP)
Department of Pathology
School of Medicine
Louisiana State University Medical Center
New Orleans, Louisiana
DO NOT REPRODUCE THIS EXERCISE.
click here to continue
©01-07-03
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C. Sue Walters, MHS, MT(ASCP)
Associate Professor
Department of Pathology
LSU Health Sciences Center
New Orleans, LA
click here to continue
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The CBC
This study exercise is the property of Carolyn Sue
Walters, MHS, MT(ASCP) and the Department of
Pathology, LSU Health Sciences Center in New
Orleans, LA. All rights are reserved. It is intended
for use solely within the LSUHSC campus network.
No part of this exercise may be reproduced, stored
in a retrieval system, or transmitted in any form or
by any means (to include but not be restricted to
electronic, mechanical, recording, and photocopying) without prior written permission from the
author.
click here to continue
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Special Acknowledgment
Special thanks is given to Angela Foley, MS,
MT(ASCP), Department of Clinical Laboratory
Sciences, LSUHSC School of Allied Health in New
Orleans, LA for the use of some of her images of
blood cells and for her assistance in the art of
creating image files…
…and to W. Douglas Scheer, PhD, Department of
Pathology, LSUHSC School of Medicine in New
Orleans, LA for converting the document for internet
access.
click here to continue
The CBC
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This is the first module of a 4-part study exercise
regarding the CBC. The four parts are entitled:
CBC – Part 1
The hemogram
CBC – Part 2
WBC differential & blood morphology
CBC – Part 3
RBC morphology & platelet estimate
CBC – Part 4
Post-test
click here to continue
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Feedback
Feedback as to the quality and usefulness of
this exercise is solicited and suggestions for
improvement are welcomed. Please forward
your remarks by E-mail [email protected]
or via US MAIL:
C. Sue Walters, MHS, MT(ASCP)
LSUHSC Department of Pathology
1901 Perdido Street
New Orleans, LA 70112
click here to continue
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Directions
The directions for navigating through the exercise are given on the next 3 pages. They are the
same as those used in the other modules of this
4-part exercise. Click on:
to visit the directions before continuing
with the exercise.
or
to bypass the directions.
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Directions, d
The following directional icons are provided
throughout the exercise for your convenience.
You can click on:
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menu
in the upper left hand corner of every page to
return to the previous page
in the upper right corner of the page to
return to the Hemogram Menu selection.
click here to continue
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Directions, d
You can click on:
in the lower right corner of the page
to continue.
Quit
in the lower right corner of the Main Menu
page to Quit (i.e., end the exercise).
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Directions, d
“Hot points” (symbols, words, phrases) have been
inserted on the pages as navigational tools and can
be identified by their “gold” color. If it’s “gold”, click
on it to move to the next text/data entry. Also, sounds
have been added in a few places for emphasis.
Caution, failure to follow the structured order of the
“hot points” may result in confusion. If you use the
mouse without placing the cursor directly on the “gold
hot point” or click without waiting for the “gold” to
appear, you may skip over vital information.
Remember, if it’s gold, click on it. Try it!
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Special Comments
This exercise has numerous images. You may
note that, when a page contains images, there
may be a rather long delay before you regain
control of the cursor. Please be patient. I think
you will find the images are worth the wait.
NOTE:
Some animation and/or interactive affects may
be lost if you attempt to replay a page by returning to the previous page and then advancing to that page again.
Now, click on the gold to begin.
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CBC – Part 1
The Complete Blood Cell Count
(CBC)
Part 1 - The Hemogram
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Does the CBC have clinical
value ?
menu
A CBC (complete blood count) is one of
the most frequently ordered laboratory
procedures. It’s useful in the diagnosis
and clinical management of numerous
diseases and disorders, such as:
anemias
leukemias & other neoplasias
infections (bacterial & viral)
inflammatory disorders (e.g., rheumatologic)
inherited anomalies
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What specimen is required?
menu
A CBC (complete blood count) can be performed
by automated electronic instruments or by
manual methods on a whole blood specimen
collected:
by
venipuncture
- in a tube containing EDTA
anticoagulant
or
capillary stick - in a vial containing a measured
volume of diluent appropriate
(e.g., finger,
for the method used
heel, ear)
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What is a CBC?
menu
A CBC is a battery of hematologic tests. The
values obtained provide valuable information
regarding the three types of blood cells found
in peripheral blood, which are red blood cells
(RBC), white blood cells (WBC), and platelets
(PLT).
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Three types of cells in peripheral
blood:
1. erythrocytes (RBC)
menu
3. platelets (PLT)
2. leukocytes (WBC)
neutrophils
eosinophils basophils lymphocytes monocytes
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menu
What information is provided by a CBC?
Basically, the CBC provides information regarding the:
 number of red cells, white cells, and platelets
in circulating peripheral blood
 frequency distribution of white blood cells
 morphologic features of the blood cells
 hemoglobin content of red blood cells
 relationship of red blood cells to total blood
volume and hemoglobin concentration
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menu
What are the components of a CBC?
In most laboratories, due to advanced technologies now available, an automated CBC is performed on a multi-channel instrument employing
a variety of techniques. It usually includes a:
1
2
Hemogram
3
General description of blood cell
morphology (WBC, RBC, and PLT)
4
Platelet estimate
Differential WBC count
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HEMOGRAM
hemogram menu
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HEMOGRAM MENU
Introduction
Total WBC Count
Corrected WBC Count
Total RBC Count
Hemoglobin
Hematocrit
Erythrocyte (RBC) Indices
Red Cell Distribution Width (RDW)
Platelet Count
Mean platelet volume
Quit
menu
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Introduction
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What is a hemogram?
menu
The hemogram components of a CBC are hematologic assays/procedures that provide useful
information regarding the red blood cells (RBC),
white blood cells (WBC), and platelets (PLT).
Automated electronic instruments are able to:
• enumerate the number of each of the three
blood cell types
• differentiate normal from abnormal cells
• provide a variety of information related to each
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What are the components of a
hemogram?
menu
WBC - total number of white blood cells per mL
of blood (SI units = per L)
RBC - total number of red blood cells per mL of
blood (SI units = per L)
HGB - average number of grams of hemoglobin
in red blood cells per dL of blood (SI
units = per L)
HCT - hematocrit or % of packed red blood cells
per unit of blood
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menu
Are the RBC indices included in a
hemogram?
The RBC indices is usually provided as part of
an automated hemogram and includes.
MCV (mean corpuscular volume)
average size (m3) of the red blood cells
MCH (mean corpuscular hemoglobin)
average hemoglobin content (mmg) in individual red blood cells
MCHC (mean corpuscular hemoglobin concentration)
average hemoglobin concentration (%) per
unit of packed red blood cells
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What additional components are
frequently included in a hemogram?
menu
Depending upon the laboratory and available
instrumentation, the hemogram may also include:
PLT - total number of platelets per mL of blood
(SI units = per L)
MPV (mean platelet volume) - average size (m3) of
individual platelets
RDW (red cell distribution width) - an index of the
variation in size of the red blood cells
Each parameter of the hemogram
will be discussed later.
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menu
Are the parameters of automated hemograms direct or indirect measurements?
Hemogram data obtained via an automated
multi-channel instrument are obtained by
one of two methods.
Direct counts/measurements
or
Indirect calculated measurements
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menu
Which components are:
Direct counts or
measurements?
WBC
RBC
HGB
PLT
MCV
Indirect calculated
measurement based on
direct measurements of
other parameters?
HCT
MPV
RDW
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menu
Are the RBC indices measured directly
or indirectly?
A combination of direct and indirect measurements are used:
MCV (direct measurement of RBC volumes
or sizes)
MCH (indirect calculation based on direct
measurements for HGB and RBC)
MCHC (indirect calculation based on direct
measurements for HGB and HCT)
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Why do we want to know whether measurements are made directly or indirectly ?
menu
In some instances, interference factors can affect
the validity of measurements.
When evaluating the validity of direct measurements, interference factors affecting only the
parameter measured must be considered.
When evaluating the validity of indirect measurements, interference factors affecting each
parameter used to calculate the indirect measurement must be considered.
Interference factors are discussed briefly at the end of
this exercise.
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How do you know if patient values
are normal or abnormal?
menu
A reference range of values for adults is provided
for each parameter of the CBC. These values,
which are generally considered to be normal, may
be gender dependent for some parameters.
CBC patient values printed out by the multichannel instruments are usually flagged when higher
or lower than the reference values.
Be aware that the reference ranges for children
are different from adults and may vary according
to age group (e.g., newborn, infants 10-17
months, child 1.5 - 4 years) .
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Are reference values the same for
every laboratory?
menu
Always refer to the reference ranges established
by the laboratory performing the CBC before
evaluating patient results. Variation among
laboratories may be seen due to different
methodologies and/or patient populations.
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Examples of reference ranges
(may vary among laboratories):
Parameter
Units
Range
WBC
x 103/mL
4.5 - 11.0
RBC
x 106/mL
m = 4.60 - 6.20
f = 4.20 - 5.40
HGB
g/dL
m = 13.5 - 18.0
f = 12.0 - 16.0
HCT
%
m = 40.0 - 54.0
f = 38.0 - 47.0
menu
menu
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Reference Ranges (d)
Parameter
Units
Range
MCV
m3
80 - 96
MCH
mmg
26 - 34*
MCHC
%
31 - 37*
PLT
x 103/mL
MPV
fL
RDW
150 - 450
6.5 - 12.0
11.6 - 14.6
* CHNO ranges
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End of Introduction
This concludes the Introduction to the
Hemogram Section. Select one of the
following:
Go to Total WBC Count, the next section, to
continue with the exercise as designed.
OR
Return to the Hemogram Menu and make an
alternate selection.
menu
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Total WBC Count
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menu
What is a total WBC count ?
A total white blood cell count is the number
of leukocytes present per unit of peripheral
blood (e.g., 6,000/mL).
WBC normally present in peripheral blood and
included in the total WBC count are mature forms
of neutrophils, eosinophils, and basophils; a few
band neutrophils (about 0-5%); lymphocytes
(mature and occasional atypical forms), and
monocytes.
view WBCs
or
continue
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WBC in Normal Blood (Adults):
mature
neutrophils
monocyte
menu
band
eosinophil
lymphocyte
basophil
*ATL (few)
*atypical lymphocyte
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In disease states, what other leukocytes
may be included in the total WBC count ?
When present in disease states, in addition to
leukocytes normally circulating in peripheral
blood, the total WBC count may also include:
• Immature leukocytes
• Leukoctyes with abnormal morphologic
alterations (which may be acquired or
inherited)
• Leukocytes associated with neoplastic
disorders (e.g., leukemia)
view WBCs
or
continue
menu
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Examples of immature WBC:
granulocytes
(various stages)
myeloblasts
lymphoblasts
monoblasts
menu
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Examples of WBC with acquired nonneoplastic abnormal alterations:
lymphocytes
neutrophils
in bacterial
infections
in viral
infections
in megaloblastic
anemias
&
with
Dohle bodies
and/or
toxic granulation
menu
&
with nuclear
hypersegmentation (> 5 lobes)
with reactive
(atypical) changes
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Examples of WBC with inherited nonneoplastic abnormal alterations:
Pelger-Huet Anomaly
menu
May-Hegglin Anomaly
&
neutrophils w/ inclusions
hyposegmented neutrophils
Alder-Reilly Anomaly
Chediak-Higashi Syndrome
&
&
neutrophils w/
abnormal granules
neutrophils and lymphocytes
w/ inclusions
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Examples of neoplastic WBC
alterations:
hairy cell leukemia
&
hairy cell lymphocytes
acute myelocytic leukemias
myeloblasts w/ Auer rod(s)
menu
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Examples of WBC in acute leukemia:
AML -myeloblasts
AMML - monoblasts
ALL - lymphoblasts
menu
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Examples of WBC in chronic leukemia:
CML - granulocytes
(various stages)
CLL - mature lymphocytes
CLL - hairy cell lymphocytes
caution
That’s a nucleated RBC…
more about NRBC later
menu
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Are leukocytes the only cells
included in the total WBC count?
Remember, all nucleated cells are included in
the total WBC count. If present, nucleated red
blood cells (e.g., in newborns and some
disease states) will also be counted.
menu
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Examples of nucleated RBC in
various stages of maturation:
proerythroblast
orthochromatophilic
erythroblast
basophilic erythroblast
polychromatophilic
erythroblast
menu
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If NRBC are included in the count,
how can the number of WBC be
determined?
menu
When nucleated red blood cells are included, the
total WBC count must be corrected for their
presence. (Refer to the Corrected Total WBC
Count Section on the Menu.)
A corrected total WBC count is determined
manually and added to the report as a “corrected
WBC”.
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Of what clinical importance are
WBC counts?
menu
WBC counts may be abnormal in disease states.
WBC counts are characteristically:
&
d
e • some viral infections
c • acute leukemias (some
r
cases/phases)
e • during chemotherapy
a
s
e
d
i
n
c
r
e
a
s
e
d
• infections (bacterial
and some viral)
• leukemoid reactions
• leukemias
• myeloproliferative
disorders
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menu
Does the total WBC count differentiate
WBC as to cell line?
No, the total WBC count is the total number of
all nucleated cells. In the case of abnormal total
WBC counts, a differential WBC count must be
performed before it can be determined which
cell line is decreased or increased.
It is also important to determine whether the
increase/decrease is a relative percent or
absolute number, which is discussed in the
Differential WBC section presented later.
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End of Total WBC Count
This concludes the Total WBC Count
Section. Select one of the following:
Go to Corrected WBC Count, the next section,
to continue with the exercise as designed.
OR
Return to the Hemogram Menu and make an
alternate selection.
menu
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Corrected WBC Count
(for presence of NRBC)
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What is the procedure for correcting
the total WBC count for NRBC ?
menu
While performing a differential WBC count on a
Wright’s or Wright’s-Giemsa stained peripheral blood
smear:
Count at least 100 WBC, e.g.,
PMNs
bands
eosinophils basophils
monocytes
lymphocytes & ATL
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…procedure for correcting the total WBC count
for NRBC continued…
menu
While counting the WBC, record the number of NRBC
observed during the count, e.g., the number of…
proerythroblast
basophilic
erythroblast
polychromatophilic
erythroblast
orthrochromatophilic
erythroblast
Then apply the following formula…
True Total WBC = Uncorrected total WBC x 100_
*100 + number of NRBC
* i.e., 100 is the number of WBC counted
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menu
An example situation that requires a
corrected (or true) total WBC count:
Patient: a 26-year-old female
¤ total uncorrected WBC count = 10,000/mL
¤ 100 WBC are counted on a Wright’s stained
peripheral blood smear…(for example)
WBC
65
¤ 25 NRBC
+
5 +
{
25
+
3
+
are observed while
counting the 100 WBC
2 = 100
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menu
The corrected (or true) WBC count
is calculated:
Uncorrected total WBC count = 10,000/mL
NRBC =
25/100 WBC
(i.e., 25 NRBC were noted per 100 WBC counted on
a stained peripheral blood smear)
True/Corrected WBC Count
10,000 x 100 =
100 + 25
1,000,000 =
125
8,000/mL
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What are the effects of NRBC on
the total WBC count?
menu
The effects of NRBC on the total WBC count
depend upon the number of NRBC present and
the total uncorrected WBC count. For example,
if the uncorrected WBC is low:
Before Correction
No. WBC
Interpretation
NRBC
/100 WBC
After Correction
No. WBC
Interpretation
5,000
Normal
1
4,950
Normal
5,000
Normal
10
4,545
Marginally
decreased
5,000
Normal
20
4,160
Decreased
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What are the effects of NRBC on
the total WBC count…
menu
If the total uncorrected WBC count is high? For
example:
Before Correction
No. WBC
Interpretation
NRBC
/100 WBC
After Correction
No. WBC
Interpretation
12,000
Increased
1
11,880
Increased
12,000
Increased
10
10,900
Marginally
increased
12,000
Increased
20
10,000
Normal
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What effects do large numbers of
NRBC have on WBC counts?
menu
For example:
Before Correction
NRBC
/100 WBC
After Correction
No. WBC
Interpretation
5,000
Normal
40
3,560
Decreased
12,000
Increased
40
8,570
Normal
50,000
Markedly High
400*
10,000
Normal
*
No. WBC
not an uncommon finding in severe anemias
Interpretation
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End of Corrected WBC Count
This concludes the Corrected WBC
Section. Select one of the following:
Go to Total RBC Count, the next section, to
continue with the exercise as designed.
OR
Return to the Hemogram Menu and make an
alternate selection.
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menu
Total RBC Count
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menu
What is the total RBC count?
The total red blood cell count is the number
of erythrocytes present per unit of peripheral
blood (e.g., /mL).
However, with the exception of platelets, all cells
(i.e., red blood cells and white blood cells) are
actually counted. In the case of healthy adults,
the inclusion of the white blood cells is not
clinically significant.
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What red blood cells are included in
a normal total RBC count?
menu
With the exception of newborns, the RBC count
on normal peripheral blood is essentially a reflection of the number of erythrocytes, i.e..
&
primarily
mature
erythrocytes
0.5 - 1.5%
polychromatophilic
erythrocytes
Erythroblasts (nucleated RBC):
are not seen in
normal blood.
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Which cells are classified as
erythrocytes?
menu
Erythrocytes are red blood cell forms without a
nucleus which includes:
mature erythrocytes
&
polychromatophilic erythrocytes
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How do erythroblasts differ from
erythrocytes?
menu
Erythroblasts are red blood cell forms with a
nucleus (for example):
orthochromatophilic
erythroblast
basophilic erythroblast
polychromatophilic
erythroblast
proerythroblast
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Are NRBC ever seen in normal
peripheral blood?
menu
Erythroblasts (NRBC) are not seen in normal adult
blood but may be seen in the peripheral blood of
newborns and in adults in disease. However, the
RBC count will reflect the number of all RBC, i.e.:
(anucleated RBC):
mature
erythrocytes
&
polychromatophilic
erythrocytes
&, if present, nucleated RBC
erythroblasts
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Why are other cells included
in the total RBC count?
Although intended to reflect only the number of
erythrocytes (red blood cells) in circulation, the RBC
count in reality includes all blood cells except normal
platelets, which are excluded because of their small
size.
menu
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Why are other cells included
in the total RBC count?
menu
Neither size criteria nor lysing techniques can
be used to exclude…
white blood cells
erythroid precursors
giant platelets
& clumps
from the RBC count because to do so would also
cause the red blood cells to be excluded.
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menu
What affect does the inclusion of other
cells have on the total RBC count?
Total WBC counts that are normal or only slightly increased will have little or no affect on the
total RBC. WBC are reported in thousands/mL
and RBC are reported in millions/mL.
For example: RBC = 4,520,000 (4.52 x 106)/mL
WBC = 8,000 (8.0 x 103)/mL
If the RBC is corrected for the presence of the
WBC, then RBC = 4,512,000 (4.51 x 106)/mL. The
difference is clinically insignificant.
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menu
Effect of increased WBC?
In disease states characterized by large numbers
of WBC, it is important to remember that they too
will be included in the RBC count. For example…
RBC = 4,000,000 (4.00 x 106)/mL
CML patient with WBC = 300,000 (300.0 x 103)/mL
If the RBC is corrected for the presence of the WBC, then
RBC = 4,000,000 – 300,000 = 3,700,000/mL.
In this case, the true RBC population may be less
than that indicated by the RBC count and may
have more clinical significance.
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menu
Effect of NRBC in disease states?
In disease states characterized by large numbers of
NRBC (e.g., thalassemia), it is important to remember
that they too will be included in the RBC count.
For example…
NRBC = 400/100 WBC (a patient with thalassemia major)
RBC = 3,000,000/mL
Total WBC uncorrected for NRBC = 100,000/mL
If the RBC is corrected for the presence of the
uncorrected WBC (which includes the NRBC), then…
RBC = 3,000,000 - 100,000 = 2,900,000/mL
In this case, the true RBC population may be less than
that indicated by the RBC count and may have more
clinical significance.
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Effects of giant platelets and platelet
clumps?
menu
When giant platelets or platelet clumps are
present in peripheral blood, they too will be
included in the RBC count. For example…
However, the number present is usually too low to cause
a clinically significant decrease in the RBC count.
It is important to remember that when platelet clumps are
seen:
• the automated platelet count (PLT) is inaccurate (the true
PLT would be higher).
• estimated platelet counts from blood smears may also
be inaccurate (the true PLT estimate would be higher).
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Of what clinical importance are RBC
counts?
menu
RBC counts (as well as hemoglobin concentration and HCT) may be abnormal in disease states.
RBC counts are characteristically:
d
&
e
c • Anemia
r
• Blood loss
e
a • Some leukemias
s
e
d
i
n
c
r
• Polycythemia vera
e
a
s
e
d
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End of Total RBC Count
This concludes the Total RBC Count
Section. Select one of the following:
Go to Hemoglobin, the section, to with the
exercise as designed.
OR
Return to the Hemogram Menu and make an
alternate selection.
menu
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Hemoglobin
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What is hemoglobin (HGB)?
menu
Hemoglobin, a conjugated protein, is the
main component of the red blood cell.
It’s major function is to transport:
O2 from lungs to tissues
and
CO2 from tissues to lungs
menu
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How does HGB transport O2 and CO2?
to
in
RBC
from
tissues
lungs O2
(eg, hand)
Hb
transported
O2
(high
tension)
back
to
lungs
in RBC
Hb
CO2
(low
tension)
and
in exchange
from
tissues
CO2
transported
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menu
Of what clinical importance are
hemoglobin values?
Abnormal hemoglobin concentrations may be
seen in disease states. Hemoglobin concentrations, as well as RBC count and HCT, are
characteristically:
d
e
c • Anemia
r
• Blood loss
e
a • Some leukemias
s
e
d
&
i
n
c
r
e
a
s
e
d
• Polycythemia vera
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End of Hemoglobin
menu
This concludes the Hemoglobin Section. Select one of the following:
Go to Hematocrit, the next section, to continue
with the exercise as designed.
OR
Return to the Hemogram Menu and make an
alternate selection.
menu
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Hematocrit
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menu
What is the hematocrit (HCT)?
The hematocrit is a reflection of the concentration of red cells, not of the total red cell
mass.
Therefore, by definition, the hematocrit is
the relative volume of packed erythrocytes
expressed as a percentage of the volume of
whole blood sample, e.g.:
40% packed cells
or 40% HCT
&
60% plasma
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menu
Of what clinical importance are
hematocrit (HCT) values?
Abnormal hematocrits may be seen in disease
states. Hematocrit values, as well as RBC count
and HGB concentrations, are characteristically:
d
e
c • Anemia
r • Blood loss
e
• Some leukemias
a
s
e
&
d
i
n
c
r • Polycythemia vera
e
a
s
e
d
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menu
How does the HCT correlate with the
RBC count when RBC are normocytic?
When erythrocytes are normocytic, there is good
correlation of the HCT and the total RBC count
(i.e., when one is low, the other is low; when one
is high, the other is high).
lymph
RBC of normal size and shape are
called normocytic. They are about
6-8mm in diameter (slightly smaller
than the nucleus of a normal, small
lymphocyte which is about 8-10 mm
in diameter).
Normal red cells are round and biconcave with a slight
central pallor.
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How does the HCT correlate with the RBC
count when the RBCs are macrocytic?
menu
In macrocytosis, because the RBC are larger
than normal,
(normocytic cells)
lymphocyte
the total RBC count may be lower than expected
based upon HCT values.
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menu
How does the HCT correlate with the RBC
count when the RBC are microcytic?
In microcytosis, because the cells are smaller
than normal,
(normocytic cells)
lymph
lymphocyte
the total RBC count may be higher than expected
based upon HCT values.
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How does the HCT correlate with the
RBC count in a mixed RBC population?
menu
The instrument electronically measures and determines a
mean volume of the cell population, e.g.,
1 normal mature RBC
2 macrocytes
3 microcytes
4 polychromatophilic erythrocyte
2
&4
8
1
2
&6
1
2
5
3
7
5 ovalocytes
6 target cells
7 RBC with inclusions
8 NRBC
Because of the variation
in cell size and volume,
correlations of RBC,
MCV, and HCT becomes
less predictable.
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menu
What are some examples of true
HCT/RBC inconsistencies?
In hydremia of pregnancy:
the HCT is low although there is no reduction in
the total number of circulating red cells.
and
In shock accompanied by hemoconcentration:
the HCT may be normal or even high though
blood loss may have caused a considerable
decrease in the total red cell mass.
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menu
What is the correlation between
HCT and hemoglobin (HGB)?
HCT (expressed in per cent) is usually roughly
3 times the HGB (expressed in g/dL).
For example:
An adult with hematocrit of 45% would normally
have a hemoglobin of about 15 g/dL.
Further discussion:
The relationships between the HCT and
total RBC count and the HCT and HGB
concentration are discussed further in the
section on RBC indices.
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End of Hematocrit
This concludes the Hematocrit Section. Select one of the following:
Go to Erythrocyte (RBC) Indices, the next
section to continue with the exercise as
designed.
OR
Return to the Hemogram Menu and make an
alternate selection.
menu
menu
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Erythrocyte (RBC) Indices
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menu
What are the erythrocyte (red blood
cell) indices?
The indices are measurements of the:
• average volume or size of red cells (MCV)
• hemoglobin content or weight in the average
red blood cell (MCH)
• hemoglobin concentration in a given volume
of red blood cells (MCHC).
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menu
Of what clinical value are the erythrocyte
(red blood cell) indices?
The indices are valuable tools in the study of anemias
because they provide an objective quantitative standard
for assessing the
 size of the red cells (MCV)
 relationship between individual blood cells and the
hemoglobin concentration (MCH)
 red blood cell population as a whole and the
hemoglobin concentration (MCHC).
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What method is used to determine the
erythrocyte (RBC) indices today?
menu
When first introduced, all of the indices (MCV,
MCH, and MCHC) were calculated values based
on accurate direct measurements of the RBC,
HGB, and HCT (packed cell volume).
Today , with the use of modern technology, it is
the MCV that is now measured directly and the
HCT that is calculated.
Let us look at the measurements included in the
indices.
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What are the measurements in the
erythrocyte indices?
menu
MCV
(mean corpuscular volume m3)
MCH
(mean corpuscular hemoglobin mmg)
MCHC
(mean corpuscular hemoglobin conc. %)
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menu
What is the MCV?
MCV is the average volume (or size) of red cells
expressed in m3 or femtoliters (fL).
Individuals with normal peripheral blood will
have a normal MCV (i.e., 80-100 m3).
The normal small mature lymphocyte, because it is
relatively consistent in size with a nucleus that is about
10-12m in diameter, is a useful tool in a visual assessment of red cell size on stained blood smears.)
lymphocyte
(nucleus 10-12m)
normal RBC
(6-8m)
10-12m
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What affect do abnormally large or
small red cells have on the MCV?
menu
Individuals with red cells that are predominantly larger
than normal (>8m diameter) will have an MCV >100 m3.
high
normal
Individuals with red cells that are predominantly smaller
than normal (<6m diameter) will have an MCV < 80 m3.
low
normal
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menu
What if there are various sizes of red cells?
E.g., macrocytic and normocytic RBC: it is important to
remember that the MCV is the average volume (or size) of
the cells. For example, if an MCV is high, it does not mean
that all of the red cells are larger. Some of the cells may
be normal or even smaller than normal. It is an indication,
however, that large cells are present in sufficient numbers
to cause an increased MCV, e.g..
x
x
x
x
x x
x
x
x
x
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menu
And conversely,
If the MCV is low, it does not necessarily mean
that all of the cells are smaller than normal. It is
an indication, however, that the number of small
cells is sufficient to cause a decreased MCV,
e.g.:
x
x
xx
x
x
x
x
x
x
x
x
x
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Does a normal MCV always indicate a normal RBC population?
menu
Again, it is important to remember that the MCV
is the average volume (or size) of the cells. A
patient with a red cell population of varying sizes
that include normocytic and/or microcytic and/or
macrocytic cells may have a normal MCV. e.g.:
x
normocytic
microcytic
macrocytic x
x
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menu
Then what is the best way to evaluate
a mixed population of RBC?
Microscopic examination of the peripheral blood
smear provides a better evaluation of MCV when
a mixed population of red cells is involved or
when interference is suspected.
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menu
Of what clinical importance are
MCV values?
MCV values may be abnormal in disease states.
E.g., MCV is characteristically elevated in:
macrocytic
anemias
x
x
and
lymph
x
may be as high as
150 m3 (or fL) if
megaloblastic
and
hypersegmented PMN
polychromasia or
reticulocytosis
(e.g., hemolytic
anemias, acute
blood loss)
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menu
Clinical importance of decreased
MCV values (continued)…
…and characteristically decreased in:
lymph
Microcytic hypochromic anemia and may be
as low as 50 m3 (or fL).
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What is the second measurement
included in the RBC indices?
In addition to the:
MCV (mean corpuscular volume m3)
There is the MCH.
menu
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What is the MCH?
menu
MCH is the content (or weight) of hemoglobin
of the average red cell (i.e., individual cells)
expressed in micromicrograms (mmg) or
picograms (pg).
The MCH is a calculated measurement based on the
values obtained for the HGB concentration and the RBC
count.
An individual whose red cells are normal (i.e., size, shape
with slight central pallor) will have a normal MCH, even if
the HGB and RBC values are decreased.
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What about individuals with a
decreased MCH?
menu
A low MCH indicates a less than normal hemoglobin content in the average individual red cell
(hypochromic erythrocytes). In some cases, the
cells may also be microcytic (< 6 mm in diameter).
lymph
x
x x
Although many RBC are
microcytic hypochromic
x
x
x
Again, this is an average.
and/or normocytic hypochromic,
some may be normochromic
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menu
Of what clinical importance are MCH
values?
MCH values may be abnormal in disease states.
E.g., MCH is characteristically elevated in:
macrocytic
anemias
x
x
and
lymph
x
may be as high as
50 mmg (or pg) if
megaloblastic
and
hypersegmented PMN
polychromasia or
reticulocytosis
(e.g., hemolytic
anemias, acute
blood loss)
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menu
Clinical importance of MCH values,
(continued)
Characteristically decreased in:
lymph
Microcytic hypochromic anemia and may be as
low as 15 mmg (or pg).
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menu
What is the third measurement
included in the RBC indices?
In addition to the:
MCV (mean corpuscular volume m3)
and
MCH(mean corpuscular hemoglobin mmg)
There is the MCHC.
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menu
What is the MCHC?
MCHC is the average hemoglobin concentration
in a given volume of packed RBC expressed
in g/dL (or %).
MCHC is based on the relationship between the HGB
concentration and the HCT and is calculated using the
values obtained for those two measurements.
An individual whose red cells are normal (i.e., size, shape
with slight central pallor) will have a normal MCHC even
if the HGB and HCT are decreased.
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menu
Of what clinical importance is the
MCHC value?
MCHC values may be abnormal in disease
states.
A true elevated MCHC is seen only in
spherocytosis.
x
x
x x
x
x x
x
x
x x
x
x
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menu
How do spherocytes differ from
normal RBCs ?
Spherocytes, (circled
in blue) are round and
have no central pallor.
Normocytic red cells (circled in red) have a slight
central pallor (about 1/3 of the cell diameter) due
to the biconcave shape
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Why is a true elevated MCHC
seen only in spherocytosis?
menu
It’s the only situation
in which the cells are
spherical and,
therefore, have a
greater capacity for
hemoglobin than
biconcave cells.
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What other disorders are characterized
by an
MCHC?
In the absence of spherocytosis, an
elevated MCHC may be an indication
of
A falsely elevated MCV and decrease in
HCT (e.g., caused by cold agglutinins)
or
Falsely elevated HGB (e.g., lipemia or
some other interfering factor).
menu
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menu
What disorders are characterized by a
MCHC?
Normal or decreased:
macrocytic anemias
Decreased:
hypochromic anemia (usually no
lower than 22 %)
Normal MCHC but reduced HGB & HCT:
normochromic anemias
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menu
How are the RBC indices calculated?
When determined by automated electronic instruments,
the MCV is a direct measurement.
A calculated indirect MCV measurment can be made
using microhematocrit values.
Calculated MCV =
Micro HCT (%) x 10
RBC (millions/mL)
MCH and MCHC are always calculated.
MCH =
HGB (g/dL) x 10
RBC (millions/mL)
MCHC =
HGB (g/dL) x 100
HCT (%)
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End of RBC Indices
This concludes the Erythrocyte (RBC) Indices
Section. Select one of the following:
Go to Red Cell Distribution Width (RDW), the next
section, to continue with the exercise as
designed.
OR
Return to the Hemogram Menu and make an
alternate selection.
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menu
Red Cell Distribution Width
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menu
What is the Red Blood Cell
Distribution Width (RDW) ?
Normally
All red cells are approximately the
same size and measure about 6-8m
in diameter.
Anisocytosis
A “generic” term used to indicate
a subjective visual assessment
of abnormal variation in size of
red cells
The RDW
An objective electronic measurement of the variation in
the size of the cells in the RBC population
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menu
How is the RDW determined?
Based on data obtained by electronic measurement of the
sizes of the red cells, the RDW is calculated by
enumerating the number of erythrocytes that are:
smaller
MCV
than the reference
(normal) cell volume (size)
normal MCV
or larger
MCV
Thus, based upon objective measurements, the
RDW provides an estimate of anisocytosis (i.e.,
variation in size of the red cells).
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menu
When are normal RDW values seen?
Normal RDW values of 11.6-14.6 (which may vary
slightly among laboratories) are seen when the
RBC are all about the same size.
(i.e., essentially
homogeneous
RBC population)
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menu
When are increased RDW values seen?
In disease, an increased RDW may be seen proportionate
to the degree of variation in size of the red blood cell
population (i.e., the greater the anisocytosis, the greater
the RDW).
e.g.
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menu
When are decreased RDW values seen?
The RDW is never decreased (i.e., less than the
lower reference value). Think about what is
being measured.
A normal RDW reflects an RBC
population in which the cells
are essentially the same size.
An increased RDW
reflects a population
with variation in size.
Those are the only two possibilities so the
RDW can never be decreased.
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menu
What causes the change in RDW?
Variability in the size of the cells in the RBC population
causes the increased RDW. The increase may reflect
an RBC population containing any combination of
abnormal and normal (or less affected) red cells, for
example…
normocytic
and
microcytic
and/or
macrocytic
menu
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What is the clinical importance of the RDW?
RDW is the most sensitive measurement involving
red cells.
RDW is the first to become abnormal (sometimes before
anemia appears).
RDW is the first to become abnormal in iron deficiency
due to chronic blood loss.
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Do the RDW and MCV measurements
provide the same information?
menu
Remember, the MCV is the average cell volume of all
circulating blood cells (for example):
normocytic,
&
macrocytic,
&
microcytic
In this case, the MCV could be within reference range after
averaging the normal size, large, and small cells included
in the measurement.
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menu
How does the MCV differ from the RDW?
Whereas the MCV is the average cell size (volume)
of a population
that may include
normocytes,
macrocytes, and
microcytes,
the RDW reflects the degree of variation in the
sizes of those blood cells. In this case, while the
MCV (average size) could possibly be within
normal limits, the RDW would be increased.
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menu
Is there any relationship at all
between the RDW and MCV?
Both the MCV and RDW are expected to be normal when the RBC population is relatively
homogeneous in size (i.e., essentially one size).
What about abnormal RBC populations?
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Can a low or high MCV be expected if the
RDW is normal?
menu
Certain conditions are characterized by red
cells that, although essentially the same size,
are smaller (or larger) than normal. In those
conditions, a normal RDW will be found even
though the MCV is low (or high).
lymph
or
lymph
homogeneously microcytic & low MCV
homogeneously macrocytic & high MCV
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Can a normal MCV be expected if the
RDW is abnormal?
menu
Even in cases where the population of blood cells
includes cells of varying size (i.e., abnormal
RDW), the MCV may be normal because it reflects
the average cell volume of all of the cells , e.g.:
2
[1] normocytic,
[2] macrocytic, and/or
1
[3] microcytic.
3
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menu
In cases where the MCV is normal and
the RDW is abnormal,
x
x
x
x
the RDW will be increased proportionately to the
number of cells smaller or larger than normal
and the degree of variability in cell size.
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menu
Examples in which both the RDW and MCV
may be normal…
RDW
MCV
Normal Normal
Conditions
good health
(homogenous
normocytic
RBC population)
Normal Normal
(homogenous
normocytic
RBC population)
chronic disease (90% of cases are
normocytic)
uremia
HbAS
HbAC
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menu
Examples in which the MCV is abnormal but
the RDW may be normal…
RDW
MCV
Conditions
Normal
Low
thalassemia minor
iron deficiency
chronic disease (10% of cases are
(homogenous
microcytic
red cells)
Normal
High
(homogenous
macrocytic
red cells)
microcytic)
aplastic anemia
myelodysplastic syndrome
anemia due to alcoholism
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menu
Examples of conditions in which the RDW
is increased and MCV is likely to be
normal…
RDW
MCV
Conditions
High
Normal
early factor deficiency
HbSS disease
HbSC disease
(average size of cells
in a heterogenous
RBC population)
menu
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Examples of conditions in which the RDW is
increased but the MCV may be decreased…
RDW
MCV
High Low
(average size of cells in
severe anemias characterized by microcytic RBC
and/or abnormalities
associated with hemolytic
alterations such as RBC
fragments)
Conditions
HbS-thalassemia
thalassemia major
HbH disease
hereditary spherocytosis
TTP
DIC
menu
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Examples of conditions in which both the
RDW and the MCV may be increased…
RDW
MCV
Conditions
High
High
vitamin B12 deficiency
folate deficiency
reticulocytosis (e.g., acute
(average size of cells in
severe anemias characterized by macrocytic
alterations in the RBC
population)
blood loss, autoimmune
hemolytic anemia
newborn (due to presence of
immature RBC)
cold agglutinins (due to false
values)
menu
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Examples of conditions with a decreased RDW
and their expected MCV.
RDW
Condition
MCV
If you were expecting to see a list of conditions,
you have not been paying attention. The RDW is
never decreased.
You may review the section on RDW or .
review RDW
or
continue
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End of Red Cell Distribution Width
This concludes the Red Cell Distribution Width
(RDW) Section. Select one of the following:
Go to Platelet Count, the next section, to continue with the exercise as designed.
OR
Return to the Hemogram Menu to review a section
on one of the parameters of the Hemogram.
menu
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Platelet Count
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menu
What is a platelet count (PLT)?
The total platelet count is the number of platelets
per given volume of peripheral blood (e.g.,
200,000/mL).
Platelets are difficult to count.
 They are small & must be differentiated
from debris.
 They have a tendency to adhere to glass,
to any foreign body, and to each other
which may cause a false low count to be
obtained.
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Are there special specimen
requirements for platelet counts?
menu
Platelet counts must be performed within:
• 3 hours after collection in an EDTA
anticoagulated tube of blood.
• 1 hour after collection in a unipette containing diluent (finger stick)
In vitro changes:
The MPV (mean platelet volume) increases after 3 hours (at least in part as a result
of the change in cell shape).
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menu
How can platelet counts be verified?
Questionable counts are verified by microscopic
examination of a stained blood smear. Examine
for:
• platelet clumps
• platelet distribution (evenly throughout smear)
• platelet estimate (1 platelet per oil immersion field
on a smear is equivalent to approximately 15,000 to
20,000 platelets)
Extremely low electronic counts are verified by
phase microscopy (i.e., manual hemacytometer
count).
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Of what clinical importance are
platelet counts?
menu
To be hemostatically effective, platelets must be
present in sufficient numbers and must be functionally normal. Platelet disorders may be classified as:
Qualitative
of platelets)
(i.e., defect in the functional ability
or
Quantitative (i.e., increase or decrease in the
number of platelets), as determined by the
platelet count.
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What disorders are associated with
a quantitative increase in platelets?
menu
Thrombocytosis, an abnormal increase in PLT,
may be due to:
Reactive thrombocytosis:
A physiologic response that may be seen as a secondary
phenomenon (eg, in trauma, hemorrhage, iron deficiency)
Temporary rise in platelets:
May be seen following splenectomy (splenic pool is
eliminated)
Autonomous (primary thrombocythemia):
A primary bone marrow disorder commonly seen in
myeloproliferative disorders. Platelets may also have
functional abnormalities.
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What disorders are associated with a
quantitative decrease in platelets?
menu
Thrombocytopenia, an abnormal decrease in
platelets may be attributed to:
Decreased production:
Due to a quantitative or hypoproliferative defect in megakaryocytes (e.g., marrow damage, replacement of normal
marrow by metastatic tumor, intrinsic marrow disease
[leukemia]),
Ineffective thrombopoiesis:
A normal number of marrow megakaryocytes, but platelet
production is decreased (e.g., megaloblastic anemias)
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menu
Quantitative platelet decreases,
(continued)
With increased destruction of platelets,
characterized by megakaryocytes in the bone
marrow and low platelet counts in peripheral
blood, PLT destruction may be due to:
Non-immune (consumptive) causes, e.g.:
• disseminated intravascular coagulation (DIC)
• thrombotic thrombocytopenic purpura (TTP)
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menu
Quantitative platelet decreases (continued)
May also be due to immune causes, e.g.:
• drug-induced immune thrombocytopenia
• acute and chronic idiopathic thrombocytopenic
purpura (ITP)
Decreases may also be due to increased spleen
pooling.
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End of Platelet Count
This concludes the Platelet Count
Section. Select one of the following:
Go to Mean Platelet Volume (MPV), the next
section, to continue with the exercise as designed.
OR
Return to the Hemogram Menu and make an
alternate selection.
menu
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Mean Platelet Volume
menu
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What is the Mean Platelet Volume (MPV)?
The mean platelet volume (MPV) is the average
volume or size of the platelets in the population.
Once the platelet count and size distribution is determined,
the mean platelet volume can be calculated from the
arithmetic mean of the extrapolated histogram.
MPV reference values are about 6.5 to 12 fL.
Normally, the platelet size varies inversely with the
platelet count.
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menu
Is platelet size affected if there is an
abnormal PLT count but normal marrow
function?
Platelet size also varies inversely with abnormal
platelet counts when there is normal marrow
function, e.g.:
PLT
Disorder
MPV
count
idiopathic thrombocytopenia
reactive thrombocytosis
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menu
Is platelet size affected if both PLT count
and marrow function are abnormal?
If there is abnormal marrow function (e.g., folate
deficiency or aplastic anemia), the MPV may be
low even though there is thrombocytopenia.
End of CBC - 1
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This concludes the Mean Platelet Volume
section and Part 1 of the study module,
“The Complete Blood Cell Count (CBC)”.
Click on Hemogram Menu to review a section.
OR
Click on
to quit CBC – Part 1
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THE END
The following are additional exercises related to
the CBC:
CBC – Part 2
WBC differential & blood morphology
CBC – Part 3
RBC morphology & platelet estimate
CBC – Part 4
Post-test
quit
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